This is an R Fuess No 15 aneroid barometer, shown in the 1940 R Fuess catalog available on this website.  The back of the case is stamped 1938.  The DRP on the face means it was patented under the Third Reich.  The dial face is about 2.5 inches in diameter, with the case being 2.75 inches in diameter.

Go to R Fuess Catalog webpage.

Go to Home Page.